has been
commonly applied, since the congress of Vienna (1814-1815), to the
European powers consulting or acting together in questions of common
interest. (See ALLIANCE and EUROPE: _HISTORY_.)

CONCERTINA, or MELODION (Fr. _concertina_, Ger. _Ziehharmonica_ or
_Bandoneon_), a wind instrument of the seraphine family with free reeds,
forming a link in the evolution of the harmonium from the mouth organ,
intermediate links being the cheng and the accordion. The concertina
consists of two hexagonal or rectangular keyboards connected by a long
expansible bellows of many folds similar to that of the accordion. The
keyboards are furnished with rows of knobs, which, on being pressed down
by the fingers, open valves admitting the air compressed by the bellows
to the free reeds, which are thus set in vibration. These free reeds
consist of narrow tongues of brass riveted by one end to the inside
surface of the keyboard, and having their free ends slightly bent, some
outwards, some inwards, the former actuated by suction when the bellows
are expanded, the latter by compression. The pitch of the note depends
upon the length and thickness of the reeds, reduction of the length
tending to sharpen the pitch of the note, while reduction of the
thickness lowers it. The bellows being unprovided with a valve can only
draw in and emit the air through the reed valves. In order to produce
the sound, the concertina is held horizontally between the hands, the
bellows being by turns compressed and expanded. The English concertina,
invented and patented by Sir Charles Wheatstone in 1829, the year of the
reputed invention of the accordion (q.v.), is constructed with a double
action, the same note being produced on compressing and expanding the
bellows, whereas in the German concertina or accordion two different
notes are given out. Concertinas are made in complete families--treble,
tenor, bass and double bass, having a combined total range of nearly
seven octaves. The compass is as follows:--

[Illustration: Treble concertina, double action]

[Illustration: Tenor concertina, single action]

[Illustration: Bass concertina, single action]

[Illustration: Double bass concertina, single action]

The timbre of the concertina is penetrating but soft, and capable of the
most delicate gradations of tone. This quality is due to a law of
acoustics governing the vibration of free reeds by means of which
_fortes_ and _pianos_ are obtained by varyin